Backplane connector and method of assembly thereof to a backplane

ABSTRACT

Back panel assembly 100 consisting of back panel 110, first header connectors 80 mounted on one side 112 of the back panel 110, and second header connectors 120 mounted on the other side 114. Due to the fact that the lengthwise edges of the pin header 124 of the second header connectors 120 fit into the spaces 82,84 of the header connectors 80, it is possible to increase connector density. Since the side wall unit 60 can be removed from the base unit 40, press-fit pins 22 can be easily replaced. The side wall unit 60 may be floatably mounted to base unit 40.

FIELD OF THE INVENTION

This invention relates to electrical connectors and more particularly toheader connectors mounted on a backplane and to the methods of assemblyof such units.

BACKGROUND OF THE INVENTION

Header connectors intended for the connection of the patterns printed ona back panel (or backplane) with external circuits by means of contactsinserted in the through holes formed in the back panel, have been usedin the art for a long time. The contacts used in such header connectorsare usually of a press-fit pin type or are of a compliant pin typehaving a spring-loaded section which can yield in the direction of thethrough hole diameter.

With reference to FIGS. 1 and 2, the design of a back panel assembly inwhich a header connector with press-fit pins is used. FIG. 1 is apartially sectioned view of a back panel assembly having headerconnectors mounted on its both surfaces with contacts extending inopposite directions; whereas FIG. 2 is a partially sectioned view of aback panel assembly having header connectors mounted on the both sidesof the back panel, with the header connectors having common contacts.

The assembly of a double-sided back panel assembly 10 shown in FIG. 1 iscarried out as follows: header connectors 16 are mounted on one side 14of the back panel 12; after that, header connectors 20 are mounted onthe other side 18 at a pre-determined pitch (see Japanese PatentDisclosure Sho 63 (1988)-228697). The assembly of a common contacts typeback panel assembly 30 shown in FIG. 2 is carried out as follows: headerconnectors 16 are mounted on one side 14 of a back panel 12; after that,housings 32 are pressed on the ends of the press-fit pins 16a protrudingfrom the other side 18 of the back panel.

Conventional back panel assemblies described above commonly have thefollowing disadvantages: in the double-sided back panel assembly shownin FIG. 1, press-fit pins 16a of the header connectors 16 mounted on theone side 14 of the back panel go through the back panel 12 and extend tothe other side 18 of the back panel 12. Therefore, it is necessary toselect such a mounting pitch of the housings 20a of the head connectors20 which are mounted to the other side 18 that they do not interferewith the press-fit pins 16a of the header connectors 16, thus limitingpotentials for an increase in the density of the header connectorsmounting.

Considerations were given to a technology making it possible to increasethe mounting density of header connectors consisting in the use ofpress-fit pins 16a which do not extend to the other side 18. For thispurpose, header connectors with press-fit pins having short contactingportions are used (not shown), and since the tips of the press-fit pinsdo not extend beyond the through hole, it is possible to achieve muchhigher mounting density of the header connectors. However, if apress-fit pin is bent and must be replaced with a good one, the bentpress-fit pin can be removed from the back panel by pushing on the tipsecured in the panel. Also, in the technology described above, in somecases, access to the tip of a damaged press-fit pin is blocked byanother connector housing making it impossible to remove the contactfrom the back panel by pressing on its tip.

Another problem relates to the fact that the assembly process of adouble-sided back panel assembly 10 shown in FIG. 1 is more difficultthan in a case when header connectors are driven only in one directionrelative to the back panel, because header connectors must be fixed toboth sides 14, 18 of the back panel 12, resulting in necessity of usingrather complicated jigs to support back panels 12 during the work.

Common-contact type back panel assembly 30 shown in FIG. 2 makes itpossible to nearly double the mounting density of the header connectorscompared to the back panel assembly 10 shown in FIG. 1. However, sincethe press-fit pins in opposed housings must have common functions, thedevices to which the press-fit pins used for signal lines are connectedat the side 14 of the back panel and to which they are connected on theother side 18, must be appropriately distributed. Therefore, thelimitations imposed on the number of signal lines are even stronger thanin the case of double-sided back panel assembly 10 shown in FIG. 1. As aresult, the scale of the circuits which can be accommodated on a backpanel with mounted header connectors is rather small, thus reducing theeffectiveness of the mounting of header connectors.

The problem to be solved by this invention is to offer a headerconnector making it possible to replace damaged contacts, withoutcompromising the density of connector mounting.

Another problem to be solved by this invention is to offer a back panelassembly with an increased effectiveness of the header connectorsmounting.

Finally, it is the intention of this invention is to offer a method ofassembly of back panel assemblies consisting of relatively easyoperations.

SUMMARY OF THE INVENTION

The header connector according to this invention includes multiplepin-shaped contacts having insertion sections to be retained in throughholes formed in the back panel; a low profile base unit retaining thesemultiple contacts passing through it; and a removable side wall unitwhich can be attached to the base unit, defining shroud side wallsaround contact sections of the multiple contacts located at the endsopposite to those to be secured in the back panel.

In one embodiment of the invention, the header connector also includes aspace formed between the side edges of the base unit and the bottomsurfaces of the side wall unit for the placement of a part of anotherconnector.

In another aspect of this invention, a back panel assembly according tothis invention includes a back panel having a number arrays of throughholes formed in it; a first header connector secured on one side of theback panel and having multiple pin-shaped contacts inserted in a firstarray of said multiple holes, a low profile base Unit in which thecontacts are retained in such a manner that they extend through the baseunit, a removable side wall unit attached to the above mentioned baseunit and running parallel to contact sections of the multiple contacts,located at the opposite end of the insertion portions, which are securedin the above mentioned base unit, and a space formed between the edgesof the base unit and the edges of the side wall unit for the placementof another connector; and a second header connector consisting of a lowprofile pin header unit retaining ends of multiple contacts passingthrough a second array of multiple through holes, which occupies a partof the space of the first header connector and which is mounted on theone side of the above mentioned back panel, and a housing having abottom wall, through which pass contact sections of the contactsretained in the pin header unit, located at the ends opposite to thosesecured in the above mentioned header unit, and side walls surroundingthese contact sections, which housing is mounted on the other side ofthe back panel.

The invention will now be explained by way of reference to the drawings,in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross-sectional views of a PRIOR ART back panelassembly using conventional header connectors, with FIG. 1 being apartially sectioned view of a back panel assembly with headerconnectors,of the type requiring the insertion of connectors from bothsides of the back panel, and FIG. 2 being a partially sectioned view ofa back panel assembly with header connectors of the type requiring theinsertion of jointly used contacts from both sides of the back panel;

FIGS. 3 to 5 are plan, front and side views of a base unit of the headerconnector according to this invention and the contacts retained in thisbase unit;

FIGS 6 is a section taken through lines 6--6 in FIG. 4;

FIGS. 7 to 10 are plan, front, bottom and side views respectively of aside wall unit of the header connector of FIGS. 3 to 6;

FIGS. 11 to 13 are views of the side wall unit of the header connector,with FIG. 11 being an enlarged view of detail as indicated in FIG. 7;FIG. 12 being a section view taken through lines 12--12 of FIG. 7; andFIG. 13 being a section view taken through lines 13--13 of FIG. 7;

FIGS. 14 to 16 are views illustrating the engagement of the lugs of thebase unit and of the recesses of the side wall unit, with FIG. 14 beinga cross-section before lugs and recesses are engaged; FIG. 15 being across section showing components in the process of engagement; and FIG.16 being a cross section showing components after the engagement iscompleted;

FIGS. 17 and 18 are views illustrating the engagement of the lugs of thebase unit and of the recesses of the side wall unit, with FIG. 17 beinga plan view showing components in the process of engagement, and FIG. 18being a cross-section showing components after the engagement iscompleted;

FIG. 19 is a plan view showing a method of restricting of the sliding ofthe side wall units by using plates secured on the back panel;

FIG. 20 is a front view of an embodiment of a header connector accordingto this invention;

FIG. 21 is a section taken through lines 21--21 of FIG. 20;

FIG. 22 is an oblique view of an embodiment of a back panel assemblyaccording to this invention;

FIG. 23 is an oblique exploded view of the back panel assembly shown inFIG. 22;

FIGS. 24 and 25 are side and cross-sectional views of the back panelassembly shown in FIG. 22; and

FIGS. 26 to 29 are cross sectional views illustrating steps of theassembly process of the back panel assembly shown in FIG. 22.

DETAILED DESCRIPTION

FIGS. 3 to 6 depict a base unit 40 of the header connector and thecontacts retained in this base unit. Two types of press-fit pins of twodifferent lengths are passed through and retained in the base unit 40.Short pins are signal press-fit pins 42, and long pins are groundingpress-fit pins 44. There are also power supply press-fit pins (notshown). As is shown in FIG. 6, slightly above the tips 42a,44a of thepress-fit pins 42,44, there are spring-loaded sections (compliant orpress-fit type) 42b,44b which can yield in the direction of the throughhole diameter, and which are wider than the diameter of the throughholes. These spring-loaded sections 42b,44b are forced into throughholes of the back panel (not shown), thus securing the base unit on theback panel. The middle section of the press-fit pin 42 has two sharptapers 42c and 42d. These tapers 42c and 42d cut into the inside wallsof the openings 48 of the base unit 40, thus securing the press-fit pins42 in the base unit 40. Similar tapers are made also on the press-fitpins 44 to secure them in the base unit 40. As shown in FIG. 3, threelugs (50a,50b,50c,52a,52b,52c) are made at each end 50 and 52 of thebase unit 40. As it will be explained below, these lugs50a,50b,50c,52a,52b,52c fit into recesses 62a,62b,62c,64a,64b,64c of theside wall unit 60 (see FIGS. 7 to 10) making it possible to attach theside wall unit 60 to, and to remove it from, the base unit 40.

FIGS. 7 to 13 depict a side wall unit 60 of the header connector. Inside wall unit 60, recesses 62a,62b,62c,64a,64b,64c are made which fitover the lugs 50a,50b,50c,52a,52b,52c formed on the base unit 40. Byputting the recesses 62a,62b,62c,64a,64b,64c over the lugs50a,50b,50c,52a,52b,52c in the order described below, side wall unit 60can be secured over the side surfaces 50, 52 of the base unit 40.

Using FIGS. 14 to 18, we will explain the order in which the recessesare fit over the lugs. In this specific case, we will explain theprocedures involving the installation of the side wall unit 60 over thebase unit 40 mounted on the back panel 110 to which pin header unit 124is attached.

When recesses 64a,64b,64c of the side wall unit 60 are being fitted overthe lugs 52a, 52b, 52c of the base unit 40, the side wall unit 60 islowered over the base unit 40 in the direction indicated by arrow "El"(see FIG. 14) until the lugs 52a, 52b, 52c come in contact with thelower surface 65 of an upper ledge above the lower ledge through whichare defined recesses 64a,64b,64c, after which the side wall unit 60 ispressed in the direction of the base unit 40 (FIG. 15). Side wall unit60 is dimensioned to provide a clearance between the side walls toreceive the base unit 40 thereinto and then subsequently be movedlaterally with respect to the base unit and parallel to back panel 110.At this time, as is shown in FIG. 17, a first locking member orprotrusion 53 made above the lug 52b fits into auxiliary recess 68 madeabove recess 64b and through the upper ledge. Then, the side wall unit60 is moved in the direction shown by arrow "F" (FIG. 15) until lug 52aabuts wall 66 of the recess 64a (FIG. 16), and protrusion 53 is movablethrough a press fit with the upper ledge until it becomes seated intoand engaged in a snap latching relationship with a second locking menberor later recess 69 (FIGS. 5 and 18) made above and between recesses64b,64c (see FIG. 12). In this position, lugs 52a, 52b and 52c of thebase unit 40 have passed through their respective recesses 64a, 64b and64c of the side wall unit 60 and lock above the lower ledge, thussecuring the side wall unit 60 to the side surface 52 of the base unit40. Protrusion 53 seated in latch recess 69 inhibits undesired lateralmovement of side wall unit 60, but protrusion 53 can be seen to includeangled corner surfaces permitting intentional dislodgment from latchrecess 69 for removal of side wall unit 60 from base unit 40. In orderto remove the side wall unit 60 from the base unit 40, the aboveprocedures are performed in the reverse order. Lugs 50a, 50b, 50c andrecesses 62a,62b,62c are handled similarly and at the same time.

However, when header connectors 80 are used for the connection of apackage (board) of electronic circuits (not shown in the drawing) havinga number of receptacle connectors, the latter are mounted on the boardwith certain allowable tolerances. On the other hand, the base units 40of the header connectors 80 are also mounted on the back panel withcertain allowable tolerances. Positioning variations caused bytolerances may result in impossibility of the joining of matchingconnectors, or in damaging some of them. For example, if we have apackage containing three receptacle connectors arrayed in a line, and ifthe central receptacle connector is shifted to the right relative to thecentral header connector 80 out of the group of three header connectorsmounted on the back panel 10 in a linear array, and if the side wallunit 60 of the header connector 80 is strongly secured on the base unit40, there is a danger that it will be impossible to connect theconnectors or a connector can be damaged. In such a situation, the sidewall unit 60 is designed in such a way that it can accommodate (by meansof floating) deviations from the correct position caused by theinsertion of a receptacle connector without damaging the connectors,thus making the joining of the connectors possible. However, protrusion53 and latch 69, as it appears in FIGS. 17 and 18, form a tightengagement, and it seems that they do not allow for floating. If thisengagement is loosened, then it will be possible for the side wall unit60 to move easier relative to the pin header 124. Thus, by separatingthe header connector 80 into the base unit 40 and the side wall unit 60,and by allowing for the floating of the side wall unit 60 relative tothe base unit 40, we can avoid the connector housing being damaged whenreceptacle connectors are joined with the header connectors according tothis invention.

If there is a danger that the loads applied to the back panel assemblyduring the insertion and removal of the back panel and during theassembly of the header connectors, can exceed the strength of theengagement of the base unit 40 and the side wall unit 60 causing theside wall unit 60 together with the base unit 40 to be shifted off theposition suitable for the connection, it is possible to supplement theretention strength of the side wall unit by plates 70, 72 and 74 shownin FIG. 19 which are attached by screws to a reinforcement frame (notshown) of the back panel 110.

FIGS. 20 and 21 depict header connector 80 with the side wall unit 60and the base unit 40 joined together. Components of the header connectorare denoted with the same numbers as in FIGS. 3 through 19. As can beseen from FIG. 21, when side wall unit 60 is attached to base unit 40,spaces 82,84 are formed between edges 54,56 of the base unit 40 andedges 61a of lengthwise walls 61 of the side wall unit 60. These spaces82,84 can be used, for example, for the insertion of the retention tipsof strip contacts of other header connectors, thus increasing themounting density of electronic devices. It is also possible to use thesespaces for the contacts of other header connectors (not shown) mountedon the other side of the back panel (not shown). Despite that the tipsof such contacts are covered by the side wall unit 60, a damaged contactof the other header connector mounted on the other side of the backpanel can be easily accessed and removed from the back panel by pushingit, after the side wall unit 60 is taken off the base unit 40.Therefore, if contacts of the other header connector are bent orotherwise damaged, they can be easily replaced. The attachment of theside wall unit 60 to the base unit 40 can be done by other means aswell, for example, by means of latching spring-loaded arms extendingfrom one side of the back panel to the other.

Next, we will explain the design of the back panel assembly according tothis invention, with reference to FIGS. 22 to 25. Components of the backpanel assembly are denoted with the same numbers as in FIGS. 3 through21. Back panel assembly 100 consists of the back panel 110, headerconnectors 80 (denoted in this invention as the first header connectors)mounted on one side 112 of the back panel 110, and header connectors 120(denoted in this invention as the 2nd header connectors) mounted on theother side 114. Since detailed explanations of the design of the headerconnector 80 were given above with reference to FIGS. 3 through 21, weomit its description here.

Header connector 120 consists of a flat pin header 124 in which ends ofmultiple press-fit pins 122 are retained, and of a housing 126 mountedon the other side 114 of the back panel. The pin header 124 is mountedon the surface 112 of the back panel 110 so that the press-fit pins 122pass through the through holes 116 of the back panel 110. Since bothlong-side edges of the pin header 124 fit into the spaces 82, 84 ofadjacent header connectors 80 (see FIG. 21), the mounting density can beincreased. Housing 126 has a bottom wall 128 and side walls 130. Bottomwall 128 has holes for the passage of contact sections 122a of press-fitpins 122, which are located at the ends opposite to those secured in pinheader 124. Side walls 130 surround the contact sections 122a. Byinstalling header connectors 80 shown by dot-and-dash lines in FIGS. 24and 25, it is possible to increase mounting density even higher.

Using FIGS. 26 to 29 for reference, we will explain the process ofassembling the back panel assembly.

First, pin headers 124 of header connectors 120 are mounted on one side112 (FIG. 27) of the back panel 110 so that press-fit pins 122 retainedin the pin header 124 pass through the through holes 116 (FIG. 26) tocontact sections 122a. At this time, connecting sections 122b of thepress-fit pins 122 are pressed in the through holes 116, thus attachingthe pin header 124 to the back panel 110.

Next, header connectors 80 are mounted on side 112 of the back panel 110between pin headers 124 so that the lengthwise edges of the pin headers124 mounted on the same side fit into the spaces 82,84 (see FIG. 21) ofthe header connector 80 (FIG. 28). Since connecting sections 42a,44aformed respectively on the stems of the press-fit pins 42 and 44 arepressed into through holes 116, the header connector 80 is attached tothe back panel 110. Since the lengthwise edges of the pin headers 124fit into the spaces 82,84 of header connectors 80, there is nointerference between side walls 61 of the header connector 80 and pinheaders 124. The length of press-fit pins 42,44 is such that their endsdo not extend beyond the other side 114 of the back panel 110. Afterheader connectors 80 are mounted on the back panel 110, housings 126 aremounted on the other side 114 of the back panel 110. During themounting, connecting sections 122a of press-fit pins 122 are passedthrough holes made in the bottom wall 128 of the housing 126. Thereforethe contacts (press-fit pins) of the header connectors 80,120 areinserted in the same direction (in this specific case, from the side 112of the back panel 110) which makes the assembly operations easier andmakes it possible to use only one jig to support the back panel duringthe assembly and to reduce the number of operations. As the result, theassembly process of the back panel assembly 100 becomes relativelyeasier.

An explanation of the operation of the present invention, and itsadvantages, will now be described. Since the side wall unit of theheader connector according to this invention is of a removable type, itcan be easily attached to and removed from the base unit. Therefore, ifheader connectors are secured on one side of a back panel and on theopposite side of the same panel, and if a tip of a contact of a headerconnector according to this invention is blocked by a side wall unit ofa header connector mounted on the other side of the back panel, it ispossible to remove said side wall unit, thus gaining access to the tipof the contact in question, and to take it out by pressing on its tip.Thus, if a contact is bent or otherwise damaged, it can be easilyreplaced with a good one. In order to replace a contact in aconventional header connector, it is necessary to form a clearance spacein front of the contact tip, which results in the presence of deadspaces and a lower density of the header connector mounting. With theheader connectors according to this invention, even if the space infront of a damaged contact tip is covered with the side wall unit of aheader connector mounted on the opposite side of the back panel, saidside wall unit can be removed, providing for an easy removal of theheader connector contact from the back panel. Therefore, contacts can beeasily replaced without reduction in the density of the mounting ofheader connectors. In addition, in the area enclosed between the edgesof the base unit and the edges of the side wall unit, a space is formedwhich can accommodate a part of other connector. Since a headerconnector can accommodate in this space a portion of another connectormounted next to it, the density of the mounting of the header connectorscan be increased.

Since, with the back panel assembly according to this invention, a partof the pin header unit of the second header connector can be mounted tothe back panel in a state when it is located in the space of the firstheader connector, it becomes possible to correspondingly increase themounting density. Moreover, the efficiency of the mounting of the headerconnectors is increased due to the fact that the first and second headerconnectors have their own contacts rather than common contacts, if thearea in the front of a contact of a second header connector is blockedby the side wall unit of the first header connector, said side wall unitcan be detached from the base unit and the contact of the second headerconnector can be easily removed from the back panel. This makes itpossible to replace bent contacts without compromising the mountingdensity of the first header connectors. Similarly, if a contact of thefirst header connector is blocked by the housing of the second headerconnector, this housing can be pulled of f the contact of the firstheader connector and the contact can be removed from the back panel.Therefore, damaged contacts of the first header connector can be easilyreplaced without compromising the mounting density of the second headerconnectors.

According to the method of assembly of the back panel assembliesaccording to this invention, the contacts of the first and the secondheader connectors are inserted in the back panel through holes from thesame side. Compared to the insertion from different sides, this methodprovides for a relatively easier operation. Since the second headerconnector can be mounted to the back panel in a state when a part of thepin header unit is contained in the space of the first header connector,it is possible to correspondingly increase the mounting density. If thearea in the front of a contact of the second header connector is blockedby the side wall unit of the first header connector, said side wall unitcan be detached from the base unit and the contact of the second headerconnector can be easily removed from the back panel. This makes itpossible to replace bent contacts without reducing the mounting densityof the first header connectors. Similarly, if a contact of the firstheader connector is blocked by the housing of a second header connector,this housing can be pulled off the contact of the first header connectorand the contact can be removed from the back panel. Therefore, bentcontacts of the first header connector can be easily replaced withoutcompromising the mounting density of the second header connectors.

As follows from the above explanations, in the header connectoraccording to this invention, it is possible to form vacant spaces bydetaching the side wall unit from the base unit. Through holescoinciding with these vacant spaces can be used for the insertion ofcontacts of other header connectors which can be easily removed ifnecessary. Therefore, in the event of bending or damage of a contact ofthe other header connector, it can be easily replaced with a good onewithout compromising the density of mounting.

By using the back panel assembly according to this invention, it ispossible to install pin headers of the second header connectors so thattheir portions come in the areas occupied by the first headerconnectors, thus making it possible to increase the mounting density bythe amount proportional to these portions. Moreover, since the contactsof the first and second header connectors are not common, the efficiencyof the mounting of the header connectors is also increased.

The method of assembly of the back panel assemblies according to thisinvention makes it possible to insert the contacts of both the first andthe second header connectors in the through holes from the same side ofthe back panel, which makes the assembly operations considerably easiercompared to assembly when the contacts are inserted from both sides ofthe back panel.

What we claim is:
 1. A header connector (80) having multiple pin-shapedcontacts (42,44) having insertion sections (42b,44b) which are retainedin through holes (116) formed in a back panel (110), and pin contactsections that extend into a cavity of said header that is perimetricallyenveloped by a shroud, comprising:a separable base unit (40) and a sidewall unit (60), said side wall unit (60) defining the shroud side walls,said base unit (40) retaining multiple contacts (42,44) passing throughit; said base unit (40) defines a bottom wall having end edges and sideedges, and said base unit includes a first locking member (53) on atleast one of said end edges; and said side wall unit has a secondlocking member (69) adjacent a bottom end edge thereof, and said sidewall unit (60) is snap latchable to said base unit (40) via said firstand second locking members; and said side wall unit provides a clearancewithin said side walls at said bottom edges thereof enabling said sidewall unit to receive thereinto said base unit and subsequently movelaterally with respect thereto parallel to the back panel, whereby saidside wall unit (60) is attachable to said base unit (40) after assemblyof said base unit to the back panel (110).
 2. The header connector asset forth in claim 1 further wherein said side wall unit (60) and saidbase unit (40) are adapted to permit removal of said side wall unit fromsaid base unit.
 3. The header connector as set forth in claim 1 furtherwherein said base unit (40) and said side wall unit (60) are snaplatchable in a lateral direction.
 4. The header connector as set forthin claim 1 further wherein said base unit (40) has opposed end edges andsaid side wall unit (60) has opposed end walls associated with said endedges, at least one end edge of said base unit (40) includes aprotrusion (53), and at least one said end wall of said side wall unit(60) includes a corresponding auxiliary recess (68) through a ledgethereof permitting passage of said protrusion (53) therethrough duringconnector assembly to a position above said ledge, and said ledgefurther including a latch recess (69) laterally of said auxiliary recess(68) within which said protrusion (53) seats to inhibit incidentallateral movement of said side wall unit after assembly.
 5. The headerconnector as set forth in claim 1 wherein said side wall unit (60) is anintegral member fabricated from insulative material.
 6. A headerconnector (80) having multiple pin-shaped contacts (42,44) havinginsertion sections (42b,44b) which are retained in through holes (116)formed in a back panel (110), and pin contact sections that extend intoa cavity of said header that is perimetrically enveloped by a shroud,comprising:a separable base unit (40) and a side wall unit (60), saidside wall unit (60) defining the shroud side walls, said base unit (40)retaining multiple contacts (42,44) passing through it, said side wallunit (60) is attachable to said base unit (40) after assembly of saidbase unit to the back panel (110); said base unit (40) defines a bottomwall having end edges and side edges, and said base unit includes afirst locking member (53) on at least one of said end edges; and saidside wall unit has a second locking member (69) adjacent a bottom endedge thereof, and said side wall unit (60) is snap latchable to saidbase unit (40) via said first and second locking members; and side edgesof said base unit (40) and bottom surfaces of said side walls of saidside wall unit (60) together define clearance spaces for the receiptthereinto of parts of other connectors mounted to the back panel (110).7. A header connector (80) having multiple pin-shaped contacts (42,44)having insertion sections (42b,44b) which are retained in through holes(116) formed in a back panel (110), and pin contact sections that extendinto a cavity of said header that is perimetrically enveloped by ashroud, comprising:a separable base unit (40) and a side wall unit (60),said side wall unit (60) defining the shroud side walls, said base unit(40) retaining multiple contacts (42,44) passing through it, said sidewall unit (60) is attachable to said base unit (40) after assembly ofsaid base unit to the back panel (110); and at least one end edge ofsaid base unit includes at least one lug extending laterally therefromspaced from the back panel, and a corresponding at least one end wall ofsaid side wall unit includes a corresponding at least one recess througha ledge extending inwardly from a bottom surface of end wall thereofadapted to permit receipt therealong of said at least one lug duringassembling of said side wall unit to said base unit until a top surfaceof said ledge passes a bottom surface of said lug permitting lateralmovement of said side wall unit to position said at least one lug alonga top surface of said ledge, securing said side wall unit to said baseunit.
 8. The header connector as set forth in claim 7 wherein both endedges of said base unit (40) each include at least one said lug(50a,50b,50c,52a,52b,52c), and both end walls of said side wall unit(60) each include a said ledge having a corresponding at least one saidrecess (62a,62b,62c,64a,64b,64c) extending therethrough, such that uponassembly of said header connector said lugs of said ends of said baseunit (40) are disposed along said top surfaces of said ledges permittingsaid lateral movement of said side wall unit (60).
 9. A header connector(80) having multiple pin-shaped contacts (42,44) having insertionsections (42b,44b) which are retained in through holes (116) formed in aback panel (110), and pin contact sections that extend into a cavity ofsaid header that is perimetrically enveloped by a shroud, comprising:aseparable base unit (40) and a side wall unit (60), said side wall unit(60) defining the shroud side walls, said base unit (40) retainingmultiple contacts (42,44) passing through it, said side wall unit (60)is attachable to said base unit (40) after assembly of said base unit tothe back panel (110); said first header connector being mounted on afirst side of a back panel, further characterized by at least one secondheader connector including a low profile pin header unit mounted on theopposite side of the back panel adjacent said base unit of said firstheader, said pin header unit retaining therein ends of second contactspassing through said through holes of a second array, and said secondheader connector further including a housing being mounted on said firstside of the back panel and having a bottom wall through which passcontact sections of said second contacts located at leading ends remotefrom said ends secured in said pin header unit, said housing includingside walls surrounding said contact sections and a space is formed by atleast one side edge of said base unit and a bottom surface of said sidewall unit of said first header connector adjacent said one side edge,defining a clearance for receipt thereinto of a complementary portion ofsaid pin header unit.
 10. The back panel assembly as set forth in claim9 further wherein said space (82,84) is formed along both side edges ofsaid base unit (40) and bottom surfaces of said side wall unit (60)along both said side edges, defining clearances for receipt thereinto ofcomplementary portions of respective said pin header units (124).
 11. Amethod of assembling a back panel assembly, comprising the stepsof:providing a back panel (110) having adjacent first and second arraysof multiple through holes (116) extending from one side (112) thereof toan opposed other side (114); providing a first header connector (80)having a low profile base unit and a removable side wall unit, saidconnector further having first contacts (42,44) having insertionsections (42b,44b) proximate to ends thereof exposed to be inserted intosaid through holes of said first array from said one side (112) of saidpanel, said low profile base unit (40) retaining said first contactspassing through it, and said removable side wall unit (60) attached tosaid base unit (40) forming a space (82,84) between said side wall unit(60) and said base unit (40) adjacent to at least one side edge of saidbase unit (40) and to a bottom surface of a side wall of said side wallunit (60) along said one side edge; providing a second header connector(120) having a low profile pin header unit (124) retaining ends ofsecond contacts (122) and a housing (126) having a bottom wall (128)through which will pass contact sections (122a) of said second contacts(122) secured in said pin header unit (124), and further having sidewalls (130) surrounding said contact sections (122a) along the otherside (114) of the back panel, after assembly of said second headerconnector (120) to the back panel (110); mounting said pin header unit(124) of said second header connector (120) to said one side (112) ofthe back panel (110) in such a manner that the said contact sections(122a) of said second contacts (122) pass through said through holes(116) of said second array and are exposed along said other side (114)of said panel; and mounting said first header connector (80) to said oneside (112) of the back panel (110) by securing said base unit (40) tosaid panel by insertion of said first contact insertion sections(42b,44b) into said first array of through holes adjacent said pinheader unit (124) in such a manner that a portion of said pin headerunit mounted on said one side, occupies said space (82,84) provided forthis purpose in said first header connector (80) adjacent to said sideedges of said base unit (40) thereof, as said insertion sections(42b,44b) of said first contacts (42,44) are inserted into said throughholes (116) of said first array.
 12. The method as set forth in claim 11further comprising the step of mounting said housing (126) of saidsecond header connector (120) to said other side (114) of the back panel(110) in such a manner that said contact sections (122a) of said secondcontacts (122) located at leading ends remote from said ends secured insaid pin header unit (124), pass through said bottom wall (128) of saidhousing (126).
 13. A header connector (80) having multiple pin-shapedcontacts (42,44) having insertion sections (42b,44b) which are retainedin through holes (116) formed in a back panel (110), and pin contactsections that extend into a cavity of said header that is perimetricallyenveloped by a shroud, comprising:a separable base unit (40) and a sidewall unit (60), said side wall unit (60) defining the shroud side walls,said base unit (40) retaining multiple contacts (42,44) passing throughit; said base unit (40) is a flat member having end edges and side edgesto be disposed adjacent and along said back panel (110); said side wallunit (60) is an integral member of insulative material; and said sidewall unit provides a clearance within said side walls at said bottomedges thereof enabling said side wall unit to receive thereinto saidbase unit and subsequently move laterally with respect thereto parallelto the back panel, whereby said side wall unit (60) is attachable tosaid base unit (40) after assembly of said base unit to the back panel(110).
 14. The header connector as set forth in claim 13 wherein saidbase unit (40) includes a first locking member (53) on a said end edge,said side wall unit (60) having opposed end walls and side walls andincludes a second locking member (69) adjacent a bottom edge of a saidend wall, said side wall unit (60) provides a bottom opening larger indimension between side walls thereof than said base unit to receive saidbase unit thereinto and permit said side wall unit to be urged in alateral direction to become snap latchable to said base unit.